Amino acid requirements of total parenteral nutrition (TPN) fed neonates: a narrative review of current knowledge and the basis for a new amino acid solution in neonatal nutrition

Abstract

Background and Objective: Globally, an estimated 11% of births, approximately 15 million babies are born preterm per year. Preterm infants have unique nutritional needs. However, gastrointestinal immaturity and congenital anomalies often preclude enteral feeding, necessitating intravenously administered total parenteral nutrition (TPN). Metabolic immaturity affects amino acid metabolism and requirements, decreases tolerance to excess intakes and ability to synthesize dispensable amino acids. Parenterally fed neonates therefore are at risk of toxicity and deficiency of amino acids which negatively affect clinical outcomes. The objectives of this narrative review were to summarize current knowledge on amino acid requirements and describe the importance of appropriate composition of amino acids in parenteral nutrition formulas for neonates. Methods: Studies published on MEDLINE between 1950 and 2020 were included if they were conducted to determine amino acid requirements, evaluate parenteral amino acid solution, splanchnic amino acid metabolism in neonates or neonatal outcomes related to amino acid intake and protein quality. Key Content and Findings: The gut is an important site of amino acid metabolism and when it is bypassed, the requirements for many amino acids are lower for TPN than for enteral feeding. Yet, the amino acid profiles in current commercial TPN formulas are based on extrapolations from plasma amino acid concentrations, human cord blood or human breast milk composition. The requirement for four amino acids in the TPN fed human neonate have been estimated and are up to 90% lower or higher than what is present in current commercial solutions. These data provide confirmation that current amino acid solutions for the neonate are inappropriate. Conclusions: We conclude that Much work is left to be done to determine the requirements for the remaining indispensable and conditionally indispensable amino acids in the parenterally fed neonate. Only then, can an optimal pattern of amino acids be combined for formulating an appropriate parenteral amino acid solution for this vulnerable patient population.